All things related to multicast

[Andrew Swan <>]

Charles R. Anderson wrote:
> Interestingly, though, our switches do support IGMPv3 snooping--it is
> the client suuport that is lacking.  And since there is no way to
> gradually migrate from IGMPv2 to IGMPv3, I can't support SSM at all
> until all the clients are upgraded.

can you elaborate on that last point?  we're running a mixed
v2-v3 network here and as far as i know everything is working
smoothly...  according to rfc 3376, the router decides
separately for each group which protocol version to use
depending on the presence of igmpv2-only hosts in the group.

and my understanding is that some routers can be configured
to ignore igmpv2 (or v1) messages for groups in 232.x.x.x so
an igmpv2-only host cannot break ssm by forcing an ssm group
into v2 compatability mode.

-Andrew